A risk-averse investor has an opportunity to invest in the following securities: Security A costs $10 today and will have a value of $25 if the market goes up and $0 if the market goes down; Security B costs $8 today and will have a value of $12 if the market goes up and $6 if the market goes down; and Security C costs $5 today and will have a value of $20 if the market goes up and $20 if the market goes down. If there is a 40 percent chance that the market will go up and the risk-free rate is zero, which security(ies) will the investor prefer?

How to calculate the expected return

the answer is B bc it generates positive expected return , but I don't know how to figure it out whether it is positive or negative